One of the Sunni extremist groups wreaking such havoc in Iraq, alongside the Islamic State in Iraq and Syria, is called the 1920 Revolution Brigades. On its seal, the motto “God shall torture them by your hands” arcs across an AK-47. Rabid invoking of the Holy One in the thick of slaughter is a mark, once again, of astounding new levels of sectarian violence in Iraq. Last week hundreds of Shiite men were coldly massacred by Sunnis near Tikrit, and dozens of Sunni prisoners, in turn, were executed in a Baqouba police station north of Baghdad. The devils are loose: gunshots to the head of helpless captives, mass decapitation, even crucifixion (“Another day,” read one headline, “another ISIS crucifixion”).

When the 21st century dawned with a savage outbreak of religiously justified violence — those Al Qaeda hijacker-pilots driving jetliners into skyscrapers while crying “God is great” — many people were perplexed that such deeds were justified by appeals to the divine. The ferocity of criminal acts reflected the belief that bloodletting was required not because of an earthly power struggle, but by the will of heaven. “God” not only justified the killing, but redoubled its brutality.

In the nations of the North Atlantic, believers and non-believers alike were appalled by this. Many insisted at first that “true religion” could have no truck with sacred violence. But the 21st-century explosion of an expressly Islamic holy war prompted a closer reading of Western history, forcing Europeans to reckon with the barbarity of their continent’s own post-Reformation religious wars, and Americans to think twice about George W. Bush’s callow call for a “crusade.”

This troubling resurgence of violence in the name of God must once again confront the conscience of every believer. How can this be? It is not enough to focus on today’s acts of “jihad,” as if the Koran were uniquely brutish. Indeed, given the global sweep of Islam, the impulse to avoid such blanket condemnation of Muslims is more important than ever. Nor should religion itself be tarred with the brush wielded by extremists, since faith-based entities accomplish massive works of mercy and justice across the world.

What the holy warriors miss is how every religion includes — within its dogma and tradition — the principles of its own self-criticism. The universal prohibition of idolatry, for example, means that anyone who kills wantonly, no matter the justification, is claiming an absolute moral power that does not belong to human beings. The worship of God carries with it the prohibition against the worship of the self as God. Religion so emphatically insists on this precisely because something in the human heart wants to be God, and when that something prevails, all hell breaks loose. The ultimate sin always comes disguised as salvation — a self-deception against which religion rails.

In this sense, what is needed even in an age marked by religious violence is not less religion, but more. Religion is its own antidote.

What is needed even in an age marked by religious violence is not less religion, but more. Religion is its own antidote.

The secular mind, having left belief behind, can foolishly imagine itself to be above all such primitive nonsense, wanting nothing to do with the deity, much less killing for it. But the terror group that calls itself the 1920 Revolution Brigades is a reminder that the scourge of violent Islam was itself sparked by that most secular of events, World War I, which destroyed the Ottoman caliphate, and first set loose the modern jihadists who claim their acts of torture originate with God. No, they originate with humans, which is why humility is due of all of us.